Applications for the use of chemical protective clothing include military, industrial, and emergency response personnel. Typical chemical/biological (“CB”) protective clothing are designed to provide protection from liquids and/or vapors that may penetrate or permeate through the materials, seams, or interfaces between clothing components.
Industrial and emergency response chemical protective clothing is designed to provide protection from a broad class of chemicals and solvents. The primary materials of choice are impermeable materials that will provide liquid penetration and permeation resistance. There are two general classes impermeable materials—reusable and limited use or disposable products. The reusable products are typically laminates made from a combination of impermeable films, rubber layers, and/or coated textiles. Limited use or disposable protective clothing consists of outer impermeable film layers laminated to nonwoven textiles; inner film layers are used in some constructions. In both the reusable and limited use product lines, the garments possess smooth outer surfaces.
Due to the frequent use of chemical protective garments for industrial or emergency response applications, economics and safe operating practices are key selection criteria. Economics are achieved through the use of thermoplastic films laminated to nonwoven textiles, creating low-cost constructions necessary for disposable applications. For reusable applications, economics are achieved through more durable constructions that are able to maintain performance features through multiple uses. In the area of safe operating practices, garments constructed with smooth surfaces are perceived to be less likely to absorb or hold contaminated substances contacted during use in contaminated environments. It is also thought that these smooth outer surfaces are more easily cleaned or decontaminated after use.
The U.S. Environmental Protection Agency (“USEPA”) has defined “Levels of Protection” (“LOP”) based on the general types of respiratory protection used in various hazardous environments. These general respiratory classifications are provided by the Occupational Safety and Health Department (“OSHA”) and the National Institute of Occupational Health (“NIOSH”). Each LOP includes general recommendations for protective clothing for different hazardous environments. Based on these guidelines, the protective clothing industry has developed garment systems suitable for the different LOP.
Level “A” is the highest level of respiratory and chemical protection and typically incorporates supplied air from a self-contained breathing apparatus (“SCBA”). Suits for Level A activities are commonly constructed from impermeable materials to insure hazardous chemical liquids and vapors do not come in contact with the wearer. These impermeable suits are designed to be fully encapsulating meaning that the wearer and respiratory protection are totally sealed within the impermeable envelope. The term “impermeable” is used in the chemical protective industry to refer to materials that have low chemical permeability to liquids and vapors including water. Because impermeable suit materials are water vapor impermeable, the wearer's own respiration causes moisture vapor to accumulate within the suit. Additionally during high workload activities, the temperature and humidity within an impermeable suit increases, resulting in wearer heat stress. As heat stress arises, the wearer's mental acuity and physical abilities decline making the use of such a suit limited to short duration activities. The fully encapsulating design of Level A suits trap heat from both the environment and the wearer.
Level “B” suits offer the next highest level of respiratory and chemical protection. These suits typically are constructed from impermeable materials and rely on SCBA respiratory protection. However, unlike the Level A suits, Level B suits are generally not a fully encapsulating ensemble. Often a Level B hood will be designed to allow the wearer's SCBA face piece to be external to the protective suit. Hands and feet are usually protected by gloves and booties which may optionally be detachable from the arms and legs of the suit, respectively. Because the majority of the wearer's body is still enclosed in an impermeable, encapsulating material, heat stress is still a critical issue in Level B protective ensembles. Similar to Level A suits, Level B suits trap heat from both the environment and the wearer and trap moisture vapor from the wearer.
Level “C” suits offer the next lower level of respiratory and chemical protection. Due to the lower level of protection required, Level “C” ensembles are non-encapsulating and designed for use with air-purifying respirators. These ensembles are offered in a range of materials from impermeable laminated films to impermeable textile composites.
Level “D” suits offer the lowest level of protection based on the OHSA recommendations. Level D suits are typically designed for use where there is no risk of respiratory exposure and the contact exposure risk is low.
As a result of the increasing threat of terrorism and the potential of more lethal chemical and biological hazards, emergency response personnel have been moving to ensembles offering higher levels of protection. In particular, the need for Level A and Level B ensembles has lead manufacturers to develop new and improved chemical protective materials. A first line of defense in most chemical protective materials is the outer most layer. This outer most layer is generally made of a liquid repelling material so that any liquid or aerosol chemical or biological hazards are repelled from the suit rather than being held in contact with the underlying barrier layers. For example, U.S. Pat. No. 4,816,330 (Freund) describes a multilayered chemical protective composite wherein the outer most layer is skived polytetrafluoroethylene in order to provide protection from chemical splashes. Likewise, U.S. Pat. No. 4,831,664 (Suda) provides “a body garment . . . formed from a laminate which includes a first layer of material adapted to provide contamination protection by means of an outer impermeable ply of synthetic polymeric/copolymeric plastic material.” And more recently, U.S. Pat. No. 5,626,947 describes an improved multilayer chemical protective composite based on an outer most layer of a liquid repelling, polymeric resin such as a fluorocarbon or polyester film.
The layers used in these multilayer constructions are usually designed to provide chemical protection by either absorbing or resisting the permeation and penetration of the chemical threat. To insure minimal absorption of chemicals, these suits have liquid repellant outer layers. And to insure protection against permeation, conventional CB protective materials are typically thick, multi-layer composites in which each layer provides protection against certain CB threats. Panels of such composite layers are generally sealed to each other to form a sealed, impermeable ensemble.
Due to the impermeable barriers used in Level A and Level B ensembles, evaporation of sweat and heat loss from wearer's body is inhibited. Moreover, the sealed nature of these suits causes any heat and/or water vapor generated by the body to be trapped within the ensemble; thereby creating a hot and humid, uncomfortable internal environment. The inability to remove heat from the body causes a wearer to experience heat buildup and heat stress. Prolonged activity in these sealed, impermeable Level A and Level B suits regularly leads to wearer heat stress. Mild heat stress is known to reduce comfort and thereby reduce cognitive and physical performance. Severe heat stress can lead to unconsciousness and/or death. Thus, the emergence of potential events requiring extended duration, higher activity work loads for Level A and Level B chemical protective suits has created a need to remove heat from the ensemble and cool the wearer.
In an attempt to reduce heat accumulation, moisture vapor permeable, chemical protective suits have been made. PCT Patent Application No. WO92/22354 (Jarnstrom) teaches reducing heat stress of wearers of impermeable suits. To overcome heat accumulation, a permeable laminate construct is provided which allows for moisture vapor transport through the suit to eliminate heat generated by the wearer, while claiming adequate chemical protection through the use of a reactive textile polymer (is this water adsorbing also?). While this approach may help reduce the temperature and humidity of the internal suit environment, it fails to provide a cooling means useful for high output workload activities. Moreover, there is no evidence to suggest that such a permeable system would be capable of meeting the stringent chemical protection requirements for Level A or Level B ensembles where toxic industrial chemical protection is needed.
U.S. Pat. No. 5,017,424 (Farnworth) describes another chemical protective bodysuit that removes heat from the wearer by water vapor transmission through the water vapor permeable suit. As with the other existing technologies described above, Farnworth requires that all the layers be water vapor permeable for the wearer to appreciate any evaporative cooling effect.
An alternate approach to enhance cooling in a moisture vapor permeable suit is via the evaporation of liquid water from the suit surface. U.S. Pat. No. 6,473,910 (Creagan) teaches that a vest lade with an outer layer comprising a water absorbing gel. When wet with liquid water, the wearer is cooled as the absorbed liquid water evaporates from the garment surface. Likewise, U.S. Pat. No. 5,263,336 (Kuramarohit) describes an outer garment comprised of perforated tubing into which water is fed. As the liquid water flows through the tubing, it exits through perforations and wets the outer textile layer. As water evaporates off the outer textile layer, a cooling effect is appreciated by the wearer. While both of these inventions teach that evaporation of water can enhance wearer cooling to the wearer of a moisture vapor permeable suit, evaporative cooling has not been used to cool the wearers of Level A and Level B chemical protective suits described above which are designed to be moisture vapor impermeable and repel liquids.
Thus, no present technology addresses the need for a high heat loss, high chemical protection, water vapor impermeable, NFPA 1994 compliant Level A or Level B or Level C type, chemical protective ensemble. The present invention meets this unique need.